Display protective film

ABSTRACT

An object of the present disclosure is to provide a protective display film famed from a fluoropolymer with hardness. The present disclosure relates to a protective display film comprising a fluoropolymer, wherein the fluoropolymer comprises, as a main component, a monomer unit represented by formula (1):wherein R1 to R4 are each independently a fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group.

TECHNICAL FIELD

The present disclosure relates to, for example, a protective displayfilm, a display comprising the protective display film, and a coatingagent for forming a protective display film.

BACKGROUND ART

A protective display film is formed on a display for the purpose ofprotection, anti-reflection, etc. Although a fluoropolymer film (PatentLiterature 1) is also considered to be a protective display film, animprovement in hardness and other physical properties is required.

CITATION LIST Patent Literature

-   PTL 1: JP2002-038075A

SUMMARY

The present disclosure includes, for example, the following embodiment.

A protective display film comprising a fluoropolymer, wherein

the fluoropolymer comprises, as a main component, a monomer unitrepresented by formula (1):

wherein R¹ to R⁴ are each independently a fluorine atom, a fluoroalkylgroup, or a fluoroalkoxy group.

Advantageous Effects

The present disclosure is capable of providing a protective display filmcomprising a fluoropolymer with hardness. The present disclosure iscapable of providing a coating agent for forming a protective displayfilm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a chart showing the transmittance at each wavelength of thefilm tested in Example 1.

DESCRIPTION OF EMBODIMENTS

The above overview of the present disclosure is not intended to describeeach of the disclosed embodiments or all of the implementations of thepresent disclosure.

The following description of the present disclosure illustratesembodiments of examples in more detail.

In several parts of the present disclosure, guidance is provided throughexamples, and these examples can be used in various combinations.

In each case, the group of examples can function as a non-exclusive andrepresentative group.

All publications, patents, and patent applications cited herein areincorporated herein by reference in their entirety.

Terms

Unless otherwise specified, the symbols and abbreviations in the presentspecification can be understood in the sense commonly used in thetechnical field to which the present disclosure pertains, according tothe context of the present specification.

In the present specification, the terms “comprise” and “contain” areused with the intention of including the terms “consisting essentiallyof” and “consisting of.”

Unless otherwise specified, the steps, treatments, or operationsdescribed in the present specification can be performed at roomtemperature. In the present specification, room temperature can mean atemperature within the range of 10° C. or higher and 40° C. or lower.

In the present specification, the phrase “C_(n)-C_(m)” (n and m are eacha number) indicates that the number of carbon atoms is n or more and mor less, as would be commonly understood by a person skilled in the art.

In the present specification, the expression “thickness” or simply “filmthickness” with respect to a film means an average film thickness. The“average film thickness” is determined as follows.

Average Film Thickness

The average film thickness is the average value of a thickness measured5 times with a micrometer. When measuring the thickness of a film itselfis difficult, such as when a film famed on a base material of asubstrate etc. cannot be peeled off, the average film thickness iscalculated by measuring the thickness of the base material before filmformation and the thickness of the base material after film formation 5times each with a micrometer, and subtracting the average value of thethickness before film formation from the average value of the thicknessafter film formation.

When the measurement cannot be performed with a micrometer, the filmthickness obtained by measuring the line profile of the cut surface of afilm to be measured with an atomic force microscope (AFM) is defined asthe average film thickness.

Specifically, the average film thickness is a value determined by themethod described in a specific example of the present disclosure.

In the present specification, the simple expression “molecular weight”means mass average molecular weight. The mass average molecular weightis determined as follows.

Mass Average Molecular Weight

The mass average molecular weight is measured by using the following GPCanalysis method. Specifically, the mass average molecular weight is avalue determined by the method described in a specific example of thepresent disclosure.

GPC Analysis Method Sample Preparation Method

A polymer is dissolved in perfluorobenzene to prepare a 2 mass % polymersolution, and the polymer solution is passed through a membrane filter(0.22 μm) to obtain a sample solution.

Measurement Method

Standard sample for measurement of molecular weight: polymethylmethacrylateDetection method: RI (differential refractometer)

In the present specification, the “indentation hardness” and“indentation elastic modulus” are determined as follows.

Indentation Hardness and Indentation Elastic Modulus

The indentation hardness (H_(IT); indentation hardness) of a sample ismeasured using an ENT-2100 ultra-fine hardness tester produced byNanotec Corporation. The indentation elastic modulus is also measured atthe same time. The test is performed by adjusting the indentation depthto be 1/10 or less of the thickness. Specifically, the indentationhardness and indentation elastic modulus are values determined by themethod described in a specific example of the present disclosure.

In the present specification, the “total light transmittance” and “haze”are determined as follows.

Measurement Method for Total Light Transmittance and Haze

The total light transmittance and haze are measured using an NDH70005PII haze meter (produced by Nippon Denshoku Industries Co., Ltd.)in accordance with JIS K7136 (haze value) and JIS K7361-1 (total lighttransmittance). A film with an average film thickness of 100 μm is usedas the sample to be measured. Specifically, the total lighttransmittance and haze are values determined by the method described ina specific example of the present disclosure.

In the present specification, the “transmittance” at each wavelength isdetermined as follows.

Transmittance at Each Wavelength

The transmittance at a specific wavelength of a sample is measured usinga Hitachi U-4100 spectrophotometer. A film with an average filmthickness of 100 μm is used as the sample. An integrating spheredetector is used as the detector. Specifically, the transmittance is avalue determined by the method described in a specific example of thepresent disclosure.

In the present specification, the “refractive index” is determined asfollows.

Refractive Index

The refractive index of a sample at 23° C. is measured with an Abberefractive index meter (NAR-1T SOLID, produced by Atago Co., Ltd.). Thewavelength is a wavelength approximate to D-line because of the use ofthe LED attached to the device. Specifically, the refractive index is avalue determined by the method described in a specific example of thepresent disclosure.

In the present specification, the “Abbe rate” at each wavelength isdetermined as follows.

Abbe Number

The Abbe number of a sample at 23° C. is measured with an Abberefractive index meter (NAR-1T SOLID, produced by Atago Co., Ltd.).Specifically, the Abbe number is a value determined by the methoddescribed in specific examples of the present disclosure.

In the present specification, the “reflectance” is determined asfollows.

Reflectance

An absolute specular reflector is attached to a Hitachi U-4100spectrophotometer, and the reflectance at 550 nm at 5° is measured.Specifically, the reflectance is a value determined by the methoddescribed in a specific example of the present disclosure.

In the present specification, the “water absorption” is determined asfollows.

Water Absorption (24° C.)

The weight of a sample that has been thoroughly dried beforehand ismeasured and set as W0. The sample is then completely immersed in waterat 24° C. that is 100 times or greater than W0 by mass. The weight ofthe sample after 24 hours is measured and set as W24. The waterabsorption is determined according to the following formula.

Water absorption (%)=100×(W24−W0)/W0

Specifically, the water absorption is a value determined by the methoddescribed in a specific example of the present disclosure.

Water Absorption (60° C.)

The weight of a sample that has been thoroughly dried beforehand ismeasured and set as W0, and then completely immersed in water at 60° C.that is 100 times or greater than W0 by mass. The weight of the sampleafter 24 hours is measured and set as W24. The water absorption isdetermined according to the following formula.

Water absorption (%)=100×(W24−W0)/W0

Specifically, the water absorption is a value determined by the methoddescribed in a specific example of the present disclosure.

In the present specification, the “tensile elastic modulus” isdetermined as follows.

Tensile Elastic Modulus

A sample (length: 30 mm, width: 5 mm, thickness: 0.1 mm) is measuredwith a DVA220 dynamic viscoelasticity measurement device produced by ITMeasurement Control Co., Ltd., under the conditions of a tensile mode, agrip width of 20 mm, a measurement temperature of 25° C. to 150° C., atemperature-increasing rate of 2° C./min, and a frequency of 1 Hz. Theelastic modulus value at 25° C. is defined as a tensile elastic modulus.Specifically, the tensile elastic modulus is a value determined by themethod described in a specific example of the present disclosure.

In the present specification, the “tensile strength” is determined asfollows.

Tensile Strength

The tensile strength of a sample is measured using an AGS-100NXautograph produced by Shimadzu Corporation. The sample is cut into adumbbell shape 5B as stated in JIS K 7162. The measurement is performedunder the conditions of a chuck-to-chuck distance of 12 mm, a crossheadspeed of 1 ram/min, and room temperature. Specifically, the tensilestrength is a value determined by the method described in a specificexample of the present disclosure.

In the present specification, the “thermal decomposition temperature” isdetermined as follows.

Thermal Decomposition Temperature

The temperatures at which the mass loss percentage of a sample becomes0.1% and 5% are measured at a temperature-increasing rate of 10°C./minute in an air atmosphere using a thermogravimetric-differentialthermal analyzer (Hitachi High-Tech Science Corporation; STA7200).Specifically, the thermal decomposition temperature is a valuedetermined by the method described in a specific example of the presentdisclosure.

In the present specification, the “glass transition temperature” isdetermined as follows.

Glass Transition Temperature (Tg)

The temperature is increased (first run), decreased, and then increased(second run) at 10° C./minute in the temperature range of 30° C. orhigher and 200° C. or lower using a DSC (differential scanningcalorimeter; Hitachi High-Tech Science Corporation, DSC7000); themidpoint of the endothermic curve in the second run is determined to bethe glass transition temperature (° C.). Specifically, the glasstransition temperature is a value determined by the method described ina specific example of the present disclosure.

In the present specification, the “coefficient of linear expansion” isdetermined as follows.

Coefficient of Linear Expansion

The temperature of a sample is increased from room temperature to 150°C. (1st up), decreased to room temperature, and then increased to 150°C. (2nd up) at 2° C./minute using a thermomechanical analyzer (TMA8310;produced by Rigaku Corporation). The average coefficient of linearexpansion at 25° C. or higher and 80° C. or lower in the 2nd up isdetermined and defined as the coefficient of linear expansion.Specifically, the coefficient of linear expansion is a value determinedby the method described in a specific example of the present disclosure.

In the present specification, unless otherwise specified, examples of“alkyl” include linear or branched C₁-C₁₀ alkyl, such as methyl, ethyl,propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl,isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, and decyl.

In the present specification, unless otherwise specified, “fluoroalkyl”is alkyl in which at least one hydrogen atom is replaced with a fluorineatom. “Fluoroalkyl” can be linear or branched fluoroalkyl.

The number of carbon atoms in “fluoroalkyl” can be, for example, 1 to12, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 6, 5, 4, 3, 2, or 1.

The number of fluorine atoms in “fluoroalkyl” can be 1 or more (e.g., 1to 3, 1 to 5, 1 to 9, 1 to 11, or 1 to the maximum substitutablenumber).

“Fluoroalkyl” includes perfluoroalkyl.

“Perfluoroalkyl” is alkyl in which all hydrogen atoms are replaced withfluorine atoms.

Examples of perfluoroalkyl include trifluoromethyl (CF₃—)pentafluoroethyl (C₂F₅—) heptafluoropropyl (CF₃CF₂CF₂—) andheptafluoroisopropyl ((CF₃)₂CF—).

Specific examples of “fluoroalkyl” include monofluoromethyl,difluoromethyl, trifluoromethyl (CF₃—), 2,2,2-trifluoroethyl (CF₃CH₂—),perfluoroethyl (C₂F₅—), tetrafluoropropyl (e.g., HCF₂CF₂CH₂—),hexafluoropropyl (e.g., (CF₃)₂CH—), perfluorobutyl (e.g.,CF₃CF₂CF₂CF₂—), octafluoropentyl (e.g., HCF₂CF₂CF₂CF₂CH₂—)perfluoropentyl (e.g., CF₃CF₂CF₂CF₂CF₂—) perfluorohexyl (e.g.,CF₃CF₂CF₂CF₂CF₂CF₂—), and the like.

In the present specification, unless otherwise specified, “alkoxy” canbe a group represented by RO—, wherein R is alkyl (e.g., C₁-C₁₀ alkyl).

Examples of “alkoxy” include linear or branched C₁-C₁₀ alkoxy, such asmethoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy,tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, hexyloxy, heptyloxy,octyloxy, nonyloxy, and decyloxy.

In the present specification, unless otherwise specified, “fluoroalkoxy”is alkoxy in which at least one hydrogen atom is replaced with afluorine atom. “Fluoroalkoxy” can be linear or branched fluoroalkoxy.

The number of carbon atoms in “fluoroalkoxy” can be, for example, 1 to12, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 6, 5, 4, 3, 2, or 1.

The number of fluorine atoms in “fluoroalkoxy” can be 1 or more (e.g., 1to 3, 1 to 5, 1 to 9, 1 to 11, or 1 to the maximum substitutablenumber).

“Fluoroalkoxy” includes perfluoroalkoxy.

“Perfluoroalkoxy” is alkoxy in which all hydrogen atoms are replacedwith fluorine atoms.

Examples of “perfluoroalkoxy” include trifluoromethoxy (CF₃O—),pentafluoroethoxy (C₂F₅O—), heptafluoropropoxy (CF₃CF₂CF₂O—), andheptafluoroisopropoxy ((CF₃)₂CFO—).

Specific examples of “fluoroalkoxy” include monofluoromethoxy,difluoromethoxy, trifluoromethoxy, 2,2,2-trifluoroethoxy (CF₃CH₂O—),perfluoroethoxy (C₂F₅O—) tetrafluoropropyloxy (e.g. HCF₂CF₂CH₂O—),hexafluoropropyloxy (e.g., (CF₃)₂CHO—), perfluorobutyloxy (e.g.,CF₃CF₂CF₂CF₂O—) octafluoropentyloxy (e.g., HCF₂CF₂CF₂CF₂CH₂O—),perfluoropentyloxy (e.g., CF₃CF₂CF₂CF₂CF₂O—), perfluorohexyloxy (e.g.,CF₃CF₂CF₂CF₂CF₂CF₂O—), and the like.

Protective Display Film

One embodiment of the present disclosure is a protective display filmcomprising a specific fluoropolymer.

The protective display film has high hardness by comprising thefluoropolymer described above.

The protective display film has high scratch resistance by comprisingthe fluoropolymer described above.

The protective display film has low reflectance by comprising thefluoropolymer described above.

The protective display film has high transparency by comprising thefluoropolymer described above.

The protective display film has low water absorption by comprising thefluoropolymer described above.

The fluoropolymer of the protective display film comprises, as a maincomponent, a monomer unit represented by formula (1):

wherein R¹ to R⁴ are each independently a fluorine atom, a fluoroalkylgroup, or a fluoroalkoxy group (this monomer unit may be referred to as“unit (1)” in the present specification).

In the present specification, phrases such as “comprising a monomer unitas a main component” mean that the percentage of the specific monomerunit is 50 mol % or more based on the total monomer units in a polymer.

Unit (1) as a monomer unit constituting the fluoropolymer may be usedsingly or in a combination of two or more.

The percentage of unit (1) may be, for example, 70 mol % or more,preferably 80 mol % or more, more preferably 90 mol % or more, andparticularly preferably 100 mol %, based on the total monomer units ofthe fluoropolymer.

In each of R¹ to R⁴, fluoroalkyl can be, for example, linear or branchedC₁-C₅ fluoroalkyl, linear or branched C₁-C₄ fluoroalkyl, linear orbranched C₁-C₃ fluoroalkyl, or C₁-C₂ fluoroalkyl.

The linear or branched C₁-C₅ fluoroalkyl is preferably linear orbranched C₁-C₅ perfluoroalkyl.

The linear or branched C₁-C₄ fluoroalkyl is preferably linear orbranched C₁-C₄ perfluoroalkyl.

The linear or branched C₁-C₃ fluoroalkyl is preferably linear orbranched C₁-C₃ perfluoroalkyl.

The C₁-C₂ fluoroalkyl group is preferably C₁-C₂ perfluoroalkyl.

In each of R¹ to R⁴, fluoroalkoxy can be, for example, linear orbranched C₁-C₅ fluoroalkoxy, linear or branched C₁-C₄ fluoroalkoxy,linear or branched C₁-C₃ fluoroalkoxy, or C₁-C₂ fluoroalkoxy.

The linear or branched C₁-C₅ fluoroalkoxy is preferably linear orbranched C₁-C₅ perfluoroalkoxy.

The linear or branched C₁-C₄ fluoroalkoxy is preferably linear orbranched C₁-C₄ perfluoroalkoxy.

The linear or branched C₁-C₃ fluoroalkoxy is preferably linear orbranched C₁-C₃ perfluoroalkoxy.

The C₁-C₂ fluoroalkoxy is preferably C₁-C₂ perfluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, linear or branched C₁-C₅fluoroalkyl, or linear or branched C₁-C₅ fluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, linear or branched C₁-C₅perfluoroalkyl, or linear or branched C₁-C₅ perfluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, linear or branched C₁-C₄fluoroalkyl, or linear or branched C₁-C₄ fluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, linear or branched C₁-C₄perfluoroalkyl, or linear or branched C₁-C₄ perfluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, linear or branched C₁-C₃fluoroalkyl, or linear or branched C₁-C₃ fluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, linear or branched C₁-C₃perfluoroalkyl, or linear or branched C₁-C₃ perfluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, C₁-C₂ fluoroalkyl, or C₁-C₂fluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, C₁-C₂ perfluoroalkyl, orC₁-C₂ perfluoroalkoxy.

R¹ to R⁴ can be each independently fluorine, trifluoromethyl,pentafluoroethyl, or trifluoromethoxy.

At least one of R¹ to R⁴ can be fluorine, and the other groups in R¹ toR⁴ can be independently C₁-C₂ perfluoroalkyl or C₁-C₂ perfluoroalkoxywhen two or more such other groups are present.

At least two of R¹ to R⁴ can be fluorine, and the other groups in R¹ toR⁴ can be independently C₁-C₂ perfluoroalkyl or C₁-C₂ perfluoroalkoxywhen two or more such other groups are present.

At least three of R¹ to R⁴ can be fluorine, and the other group in R¹ toR⁴ can be C₁-C₂ perfluoroalkyl or C₁-C₂ perfluoroalkoxy.

At least three of R¹ to R⁴ can be fluorine atoms, and the other group inR¹ to R⁴ can be C₁-C₂ perfluoroalkyl.

R¹ to R⁴ can be all fluorine atoms.

Unit (1) can be a monomer unit represented by the following formula(1-1) (this unit may be referred to as “unit (1-1)” in the presentspecification).

In the formula, R¹ is a fluorine atom, a fluoroalkyl group, or afluoroalkoxy group.

Unit (1-1) as a monomer unit constituting the fluoropolymer may be usedsingly or in a combination of two or more.

In unit (1-1), R¹ can be fluorine, linear or branched C₁-C₅ fluoroalkyl,or linear or branched C₁-C₅ fluoroalkoxy.

In unit (1-1), R¹ can be fluorine, linear or branched C₁-C₅perfluoroalkyl, or linear or branched C₁-C₅ perfluoroalkoxy.

In unit (1-1), R¹ can be fluorine, linear or branched C₁-C₄ fluoroalkyl,or linear or branched C₁-C₄ fluoroalkoxy.

In unit (1-1), R¹ can be fluorine, linear or branched C₁-C₄perfluoroalkyl, or linear or branched C₁-C₄ perfluoroalkoxy.

In unit (1-1), R¹ can be fluorine, linear or branched C₁-C₃ fluoroalkyl,or linear or branched C₁-C₃ fluoroalkoxy.

In unit (1-1), R¹ can be fluorine, linear or branched C₁-C₃perfluoroalkyl, or linear or branched C₁-C₃ perfluoroalkoxy.

In unit (1-1), R¹ can be fluorine, C₁-C₂ fluoroalkyl, or C₁-C₂fluoroalkoxy.

In unit (1-1), R¹ can be fluorine, C₁-C₂ perfluoroalkyl, or C₁-C₂perfluoroalkoxy.

In unit (1-1), R¹ can be fluorine, trifluoromethyl, pentafluoroethyl, ortrifluoromethoxy.

In unit (1-1), R¹ can be C₁-C₂ perfluoroalkyl or C₁-C₂ perfluoroalkoxy.

In unit (1-1), R¹ can be C₁-C₂ perfluoroalkyl.

Preferred examples of unit (1-1) include a monomer unit represented bythe following formula (1-11) (this monomer unit may be referred to as“unit (1-11)” in the present specification).

The fluoropolymer may comprise a fluoroolefin unit in addition to unit(1).

The fluoroolefin unit may be used singly or in a combination of two ormore.

The percentage of the fluoroolefin unit can be 50 mol % or less,preferably 30 mol % or less, more preferably 20 mol % or less, even morepreferably 10 mol % or less, and particularly preferably 0 mol %, basedon the total monomer units.

The fluoroolefin unit is a monomer unit that is formed afterpolymerization of a monomer containing fluorine and a carbon-carbondouble bond.

The atoms constituting the fluoroolefin unit may be only fluorine,halogen other than fluorine, carbon, hydrogen, and oxygen.

The atoms constituting the fluoroolefin unit may be only fluorine,halogen other than fluorine, carbon, and hydrogen.

The atoms constituting the fluoroolefin unit may be only fluorine,carbon, and hydrogen.

The atoms constituting the fluoroolefin unit may be only fluorine andcarbon.

The fluoroolefin unit includes at least one unit selected from the groupconsisting of a fluorine-containing perhaloolefin unit, a vinylidenefluoride unit (—CH₂—CF₂—), a trifluoroethylene unit (—CFH—CF₂—), apentafluoropropylene unit (—CFH—CF(CF₃)—, —CF₂—CF(CHF₂)—), a1,1,1,2-tetrafluoro-2-propylene unit (—CH₂—CF(CF₃)—), and the like.

The fluorine-containing perhaloolefin unit is a monomer unit that isformed after polymerization of a monomer containing fluorine and acarbon-carbon double bond, and optionally halogen other than fluorine.

The fluorine-containing perhaloolefin unit includes at least one memberselected from the group consisting of a chlorotrifluoroethylene unit(—CFCl—CF₂—), a tetrafluoroethylene unit (—CF₂—CF₂—), ahexafluoropropylene unit (—CF₂—CF(CF₃)—), a perfluoro(methyl vinylether) unit (—CF₂—CF(OCF₃)—), a perfluoro(ethyl vinyl ether) unit(—CF₂—CF(OC₂F₅)—), perfluoro(propyl vinyl ether) unit(—CF₂—CF(OCF₂C₂F₅)—) perfluoro(butyl vinyl ether) unit(—CF₂—CF(O(CF₂)₂C₂F₅)—), and a perfluoro(2,2-dimethyl-1,3-dioxol) unit(—CF—CAF— (wherein A represents a perfluorodioxolane ring formed withthe adjacent carbon atom shown in the formula, with two trifluoromethylbonded to the carbon atom at position 2 of the dioxolane ring).

The fluoroolefin unit includes at least one member selected from thegroup consisting of a chlorotrifluoroethylene unit, atetrafluoroethylene unit, a hexafluoropropylene unit, a perfluoro(methylvinyl ether) unit, and a perfluoro(propyl vinyl ether) unit.

The fluoropolymer may further contain one or more other monomer units inaddition to unit (1) and the fluoroolefin unit. However, it ispreferable to contain no other monomer units. The other monomer unitsinclude CH₂═CHRf (wherein Rf represents a C₁-C₁₀ fluoroalkyl group)units, alkyl vinyl ether units (e.g., a cyclohexyl vinyl ether unit,ethyl vinyl ether unit, butyl vinyl ether unit, and methyl vinyl etherunit), alkenyl vinyl ether units (e.g., a polyoxyethylene allyl etherunit and ethyl allyl ether unit), organosilicon compound units having areactive α,β-unsaturated group (e.g., a vinyltrimethoxysilane unit,vinyltriethoxysilane unit, and a vinyltris(methoxyethoxy)silane unit),acrylic ester units (e.g., a methyl acrylate unit and ethyl acrylateunit), methacrylic ester units (e.g., a methyl methacrylate unit andethyl methacrylate unit), vinyl ester units (e.g., a vinyl acetate unit,vinyl benzoate unit, and a VeoVA (vinyl ester produced by Shell plc)unit), and the like.

The percentage of the other monomer units may be, for example, 0 mol %or more and 20 mol % or less, or 0 mol % or more and 10 mol % or less,based on the total monomer units.

The fluoropolymer preferably has a glass transition temperature (Tg) of110° C. or higher, more preferably 110° C. or higher and 300° C. orlower, even more preferably 120° C. or higher and 300° C. or lower, andparticularly preferably 125° C. or higher and 200° C. or lower. A glasstransition temperature within these ranges is advantageous in terms ofhigh bending durability of the protective display film in, for example,a flexible display comprising a protective display film.

The fluoropolymer has a mass average molecular weight of, for example,10,000 or more and 1,000,000 or less, preferably 30,000 or more and500,000 or less, and more preferably 50,000 or more and 300,000 or less.A molecular weight within these ranges is advantageous in terms ofdurability.

A fluoropolymer can be produced, for example, by polymerizing one ormore monomers corresponding to one or more monomer units constitutingthe fluoropolymer by an appropriate polymerization method. For example,a fluoropolymer can be produced by polymerizing one or more monomerscorresponding to unit (1).

A fluoropolymer can also be produced by polymerizing one or moremonomers corresponding to unit (1), optionally with at least one monomerselected from the group consisting of fluoroolefins and other monomers.

A person skilled in the art would be able to understand monomerscorresponding to the monomer units constituting a fluoropolymer. Forexample, a monomer corresponding to unit (1) is a compound representedby formula (M1):

wherein R¹ to R⁴ are as defined above (this compound may be referred toas “monomer (M1)” in the present specification).

For example, a monomer corresponding to unit (1-1) is a compoundrepresented by formula (M1-1):

wherein R¹ is a fluorine atom, a fluoroalkyl group, or a fluoroalkoxygroup (this compound may be referred to as “monomer (M1-1)” in thepresent specification).

For example, the monomer corresponding to unit (1-11) is a compoundrepresented by formula (M1-11):

(this compound may be referred to as “monomer (M1-11)” in the presentspecification).

The fluoroolefins for use may be monomers corresponding to thefluoroolefin units mentioned above. For example, the monomerscorresponding to the tetrafluoroethylene unit, hexafluoropropylene unit,and vinylidene fluoride unit are tetrafluoroethylene (CF₂═CF₂),hexafluoropropylene (CF₃CF═CF₂), and vinylidene fluoride (CH₂═CF₂),respectively. Thus, the details regarding fluoroolefins would be able tobe understood by a person skilled in the art from the description of thecorresponding fluoroolefin units.

For example, the fluoroolefin may be at least one member selected fromthe group consisting of fluorine-containing perhaloolefins, vinylidenefluoride, trifluoroethylene, pentafluoropropylene, and1,1,1,2-tetrafluoro-2-propylene. Preferably, the fluoroolefin may be atleast one member selected from the group consisting ofchlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene,perfluoro(methyl vinyl ether), and perfluoro(propyl vinyl ether).

The fluorine-containing perhaloolefin may be at least one memberselected from the group consisting of chlorotrifluoroethylene,tetrafluoroethylene, hexafluoropropylene, perfluoro(methyl vinyl ether),perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether),perfluoro(butyl vinyl ether), and perfluoro(2,2-dimethyl-1,3-dioxol).

The other monomers for use may be monomers corresponding to the othermonomer units mentioned above. Thus, the details regarding the othermonomers would be able to be understood by a person skilled in the artfrom the description of the corresponding other monomer units.

The polymerization method includes, for example, a method of usingappropriate amounts of monomers corresponding to the monomer units thatconstitute the fluoropolymer, with the monomers being optionallydissolved or dispersed in a solvent (e.g., an aprotic solvent) and apolymerization initiator being optionally added, and performingpolymerization (e.g., radical polymerization, bulk polymerization,solution polymerization, suspension polymerization, dispersionpolymerization, or emulsion polymerization).

The polymerization method is preferably solution polymerization becausesolution polymerization can produce a high-concentration solution of thefluoropolymer and thereby achieve a high manufacturing yield, and isadvantageous for the formation of a thick film and purification.Therefore, the fluoropolymer is preferably produced by solutionpolymerization. The fluoropolymer is more preferably produced bysolution polymerization in which one or more monomers are polymerized inthe presence of an aprotic solvent.

The solvent for use in solution polymerization of the fluoropolymer ispreferably an aprotic solvent. The amount of aprotic solvent for use inthe production of the fluoropolymer is, for example, 80 mass % or less,less than 80 mass %, 75 mass % or less, 70 mass % or less, 35 mass % ormore and 95 mass % or less, 35 mass % or more and 90 mass % or less, 35mass % or more and 80 mass % or less, 35 mass % or more and 70 mass % orless, 35 mass % or more and less than 70 mass %, or 60 mass % or moreand 80 mass % or less, based on the sum of the mass of the monomers andthe mass of the solvent. The amount can be preferably 35 mass % or moreand less than 80 mass %, more preferably 40 mass % or more and 75 mass %or less, and particularly preferably 50 mass % or more and 70 mass % orless.

The aprotic solvent for use in the polymerization of fluoropolymers canbe, for example, at least one member selected from the group consistingof perfluoroaromatic compounds, perfluorotrialkylamines,perfluoroalkanes, hydrofluorocarbons, perfluorocyclic ethers,hydrofluoroethers, and olefin compounds containing at least one chlorineatom.

The perfluoroaromatic compound is, for example, a perfluoroaromaticcompound optionally having one or more perfluoroalkyl groups. Thearomatic ring of the perfluoroaromatic compound can be at least one ringselected from the group consisting of a benzene ring, a naphthalenering, and an anthracene ring. The perfluoroaromatic compound can haveone or more (e.g., one, two, or three) aromatic rings.

The perfluoroalkyl group as a substituent is, for example, linear orbranched, C₁-C₆, C₁-C₅, or C₁-C₄ perfluoroalkyl, and preferably linearor branched C₁-C₃ perfluoroalkyl.

The number of substituents is, for example, one to four, preferably oneto three, and more preferably one or two. When a plurality ofsubstituents are present, the substituents may be the same or different.

Examples of perfluoroaromatic compounds include perfluorobenzene,perfluorotoluene, perfluoroxylene, and perfluoronaphthalene.

Preferred examples of perfluoroaromatic compounds includeperfluorobenzene and perfluorotoluene.

The perfluorotrialkylamine is, for example, an amine substituted withthree linear or branched perfluoroalkyl groups. The number of carbonatoms of each perfluoroalkyl group is, for example, 1 to 10, preferably1 to 5, and more preferably 1 to 4. The perfluoroalkyl groups can be thesame or different, and are preferably the same.

Examples of perfluorotrialkylamines include perfluorotrimethylamine,perfluorotriethylamine, perfluorotripropylamine,perfluorotriisopropylamine, perfluorotributylamine,perfluorotri-sec-butylamine, perfluorotri-tert-butylamine,perfluorotripentylamine, perfluorotriisopentylamine, andperfluorotrineopentylamine.

Preferred examples of perfluorotrialkylamines includeperfluorotripropylamine and perfluorotributylamine.

The perfluoroalkane is, for example, a linear, branched, or cyclicC₃-C₁₂ (preferably C₃-C₁₀, more preferably C₃-C₆) perfluoroalkane.

Examples of perfluoroalkanes include perfluoropentane,perfluoro-2-methylpentane, perfluorohexane, perfluoro-2-methylhexane,perfluoroheptane, perfluorooctane, perfluorononane, perfluorodecane,perfluorocyclohexane, perfluoro(methylcyclohexane),perfluoro(dimethylcyclohexane) (e.g.,perfluoro(1,3-dimethylcyclohexane)), and perfluorodecalin.

Preferred examples of perfluoroalkanes include perfluoropentane,perfluorohexane, perfluoroheptane, and perfluorooctane.

The hydrofluorocarbon is, for example, a C₃-C₈ hydrofluorocarbon.Examples of hydrofluorocarbons include CF₃CH₂CF₂H, CF₃CH₂CF₂CH₃,CF₃CHFCHFC₂F₅, 1,1,2,2,3,3,4-heptafluorocyclopentane,CF₃CF₂CF₂CF₂CH₂CH₃, CF₃CF₂CF₂CF₂CF₂CHF₂, and CF₃CF₂CF₂CF₂CF₂CF₂CH₂CH₃.

Preferred examples of hydrofluorocarbons include CF₃CH₂CF₂H andCF₃CH₂CF₂CH₃.

The perfluorocyclic ether is, for example, a perfluorocyclic etheroptionally having one or more perfluoroalkyl groups. The ring of theperfluorocyclic ether may be a 3- to 6-membered ring. The ring of theperfluorocyclic ether may have one or more oxygen atoms as aring-constituting atom.

The ring preferably has one or two oxygen atoms, and more preferably oneoxygen atom.

The perfluoroalkyl group as a substituent is, for example, linear orbranched C₁-C₆, C₁-C₅, or C₁-C₄ perfluoroalkyl. The perfluoroalkyl groupis preferably linear or branched C₁-C₃ perfluoroalkyl.

The number of substituents is, for example, one to four, preferably oneto three, and more preferably one or two. When a plurality ofsubstituents are present, they may be the same or different.

Examples of perfluorocyclic ethers include perfluorotetrahydrofuran,perfluoro-5-methyltetrahydrofuran, perfluoro-5-ethyltetrahydrofuran,perfluoro-5-propyltetrahydrofuran, perfluoro-5-butyltetrahydrofuran, andperfluorotetrahydropyran.

Preferred examples of perfluorocyclic ethers includeperfluoro-5-ethyltetrahydrofuran and perfluoro-5-butyltetrahydrofuran.

The hydrofluoroether is, for example, a fluorine-containing ether.

The hydrofluoroether preferably has a global warming potential (GWP) of400 or less, and more preferably 300 or less.

Examples of hydrofluoroethers include CF₃CF₂CF₂CF₂OCH₃, CF₃CF₂CF(CF₃)OCH₃, CF₃CF(CF₃) CF₂OCH₃, CF₃CF₂CF₂CF₂OC₂H₅, CF₃CH₂OCF₂CHF₂,C₂F₅CF(OCH₃)C₃F₇, (CF₃)₂CHOCH₃, (CF₃)₂CFOCH₃, CHF₂CF₂OCH₂CF₃,CHF₂CF₂CH₂OCF₂CHF₂, CF₃CHFCF₂OCH₃, CF₃CHFCF₂OCF₃, trifluoromethyl1,2,2,2-tetrafluoroethyl ether (HFE-227me), difluoromethyl1,1,2,2,2-pentafluoroethyl ether (HFE-227mc), trifluoromethyl1,1,2,2-tetrafluoroethyl ether (HFE-227pc), difluoromethyl2,2,2-trifluoroethyl ether (HFE-245mf), 2,2-difluoroethyltrifluoromethylether (HFE-245pf), 1,1,2,3,3,3-hexafluoropropylmethyl ether(CF₃CHFCF₂OCH₃), 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether(CHF₂CF₂OCH₂CF₃), and 1,1,1,3,3,3-hexafluoro-2-methoxypropane(CF₃)₂CHOCH₃).

Preferred examples of hydrofluoroethers include CF₃CF₂CF₂CF₂OCH₃,CF₃CF₂CF₂CF₂OC₂H₅, CF₃CH₂OCF₂CHF₂, and C₂F₅CF(OCH₃)C₃F₇.

The hydrofluoroether is preferably a compound represented by thefollowing formula (B1):

R²¹—O—R²²  (B1),

wherein R²¹ is linear or branched perfluorobutyl and R²² is methyl orethyl.

The olefin compound containing at least one chlorine atom is a C₂-C₄(preferably C₂-C₃) olefin compound containing at least one chlorine atomin its structure. The olefin compound containing at least one chlorineatom is a compound in which at least one of the hydrogen atoms bonded tothe carbon atoms in a C₂-C₄ hydrocarbon having one or two (preferablyone) carbon-carbon double bonds (C═C) is replaced with chlorine. Acompound in which at least one of the hydrogen atoms bonded to twocarbon atoms constituting the carbon-carbon double bond in a C₂-C₄hydrocarbon is replaced with chlorine is preferred.

The number of chlorine atoms is one to the maximum substitutable number.The number of chlorine atoms may be, for example, one, two, three, four,or five.

The olefin compound containing at least one chlorine atom may contain atleast one (e.g., one, two, three, four, or five) fluorine atom.

Examples of olefin compounds containing at least one chlorine atominclude CH₂═CHCl, CHCl═CHCl, CCl₂═CHCl, CCl₂═CCl₂, CF₃CH═CHCl,CHF₂CF═CHCl, CFH₂CF═CHCl, CF₃CCl═CFCl, CF₂HCl═CFCl, and CFH₂Cl═CFCl.

Preferred examples of olefin compounds containing at least one chlorineatom include CHCl═CHCl, CHF₂CF═CHCl, CF₃CH═CHCl, and CF₃CCl═CFCl.

As the aprotic solvent, a hydrofluoroether is preferable because it hasless environmental impact during use and polymers can be dissolved athigh concentrations in it.

Preferred examples of polymerization initiators used in production ofthe fluoropolymer include di-n-propyl peroxydicarbonate, diisopropylperoxydicarbonate, diisobutyryl peroxide,di(ω-hydro-dodecafluoroheptanoyl)peroxide,di(ω-hydro-hexadecafluorononanoyl)peroxide,ω-hydro-dodecafluoroheptanoyl-ω-hydro-hexadecafluorononanoyl-peroxide,benzoyl peroxide, tert-butyl peroxypivalate, tert-hexyl peroxypivalate,ammonium persulfate, sodium persulfate, and potassium persulfate.

Particularly preferred examples of polymerization initiators includedi-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate,diisobutyryl peroxide, di(ω-hydro-dodecafluoroheptanoyl)peroxide,benzoyl peroxide, tert-butyl peroxypivalate, tert-hexyl peroxypivalate,and ammonium persulfate.

The amount of the polymerization initiator for use in the polymerizationreaction can be, for example, 0.0001 g or more and 0.05 g or less,preferably 0.0001 g or more and 0.01 g or less, and more preferably0.0005 g or more and 0.008 g or less, per gram of all of the monomerssubjected to the reaction.

The temperature of the polymerization reaction can be, for example, −10°C. or higher and 160° C. or lower, preferably 0° C. or higher and 160°C. or lower, and more preferably 0° C. or higher and 100° C. or lower.

The reaction time for the polymerization reaction is preferably 0.5hours or more and 72 hours or less, more preferably 1 hour or more and48 hours or less, and even more preferably 3 hours or more and 30 hoursor less.

The polymerization reaction can be performed in the presence or absenceof an inert gas (e.g., nitrogen gas), and preferably in the presence ofan inert gas.

The polymerization reaction can be performed under reduced pressure,atmospheric pressure, or increased pressure.

The polymerization reaction can be performed by adding one or moremonomers to an aprotic solvent containing a polymerization initiator andsubjecting it to polymerization conditions. The polymerization reactioncan also be performed by adding a polymerization initiator to an aproticsolvent containing one or more monomers and subjecting it topolymerization conditions.

The fluoropolymer produced by the polymerization reaction may bepurified, if desired, by a conventional method, such as extraction,dissolution, concentration, filtration, precipitation, reprecipitation,dehydration, adsorption, or chromatography, or a combination of thesemethods. Alternatively, a solution of the fluoropolymer produced by thepolymerization reaction, a dilute solution thereof, or a mixture of thesolution with other optional components or the like may be dried orheated (e.g., 30° C. or higher and 150° C. or lower) to form aprotective display film containing the fluoropolymer.

The content of the fluoropolymer in the protective display film can be,for example, 50 mass % or more and 100 mass % or less, preferably 60mass % or more and 100 mass % or less, more preferably 80 mass % or moreand 100 mass % or less, and particularly preferably 90 mass % or moreand 100 mass % or less, based on the total mass of the protectivedisplay film.

The protective display film may comprise other components in addition tothe fluoropolymer. Such other components may be known componentsaccording to the use of the protective display film, such as colorants,light-diffusing agents, various fillers (e.g., conductivity-impartingfillers), plasticizers, viscosity modifiers, flexibilizers,light-resistant stabilizers, reaction inhibitors, and adhesionpromoters.

The protective display film may comprise other components in appropriateamounts as long as the effects of the present disclosure are obtained.The content of the other components can be, for example, 0 mass % ormore and 50 mass % or less, preferably 0 mass % or more and 40 mass % orless, more preferably 0 mass % or more and 20 mass % or less, andparticularly preferably 0 mass % or more and 10 mass % or less, based onthe total mass of the protective display film.

The protective display film can be produced, for example, by drying orheating a liquid obtained by dissolving or dispersing the fluoropolymerin a solvent to thus remove the solvent from the liquid. Preferably, theprotective display film can be produced by removing the solvent from thecoating agent of the present disclosure described below.

The thickness of the protective display film can be appropriatelyselected according to the required function etc. of the film. Thethickness can be, for example, 10 nm or more, 10 nm or more and 1000 μmor less, 30 nm or more and 500 μm or less, or 50 nm or more and 500 μmor less, and preferably 100 nm or more and 500 μm or less, morepreferably 500 nm or more and 300 μm or less, even more preferably 800nm or more and 200 μm or less, and particularly preferably 10 nm or moreand 200 μm or less. An average film thickness within these ranges isadvantageous in tams of durability.

The protective display film, which comprises the fluoropolymer, has highindentation hardness and thus has excellent scratch resistance. Theindentation hardness of the protective display film can be, for example,250 N/mm² or more and 1000 N/mm² or less, preferably 300 N/mm² or moreand 800 N/mm² or less, and more preferably 350 N/mm² or more and 600 N.

The indentation elastic modulus of the protective display film can be,for example, 2.5 GPa or more and 10 GPa or less, preferably 2.5 GPa ormore and 8 GPa or less, and more preferably 2.5 GPa or more and 6 GPa orless.

Since the fluoropolymer has high permeability, the protective displayfilm can be used as an optical material. The total light transmittanceof the protective display film can be, for example, 90% or more and 99%or less, preferably 92% or more and 99% or less, and more preferably 94%or more and 99%& or less.

Since the fluoropolymer also has high ultraviolet transmittance, theprotective display film can also be used as an optical material forultraviolet light. The transmittance of the protective display film at193 nm or more and 410 nm or less can be, for example, 60% or more andpreferably 70% or more.

The refractive index of the protective display film can be, for example,1.25 or more and 1.4 or less, preferably 1.29 or more and 1.37 or less,and more preferably 1.3 or more and 1.36 or less.

The Abbe number of the protective display film can be, for example, 80or more and 100 or less, preferably 85 or more and 96 or less, and morepreferably 87 or more and 94 or less.

The water absorption (24° C.) of the protective display film can be, forexample, 0.1% or less, preferably 0.05% or less, and more preferably0.01%.

The protective display film has high hardness, excellent lightpermeability, etc. and is thus capable of protecting the display surfacewhen provided on the surface of a display.

Display

One embodiment of the present disclosure is a display comprising theprotective display film. The type of display is not limited as long asthe protective display film is applicable. The display includes not onlydisplays designed to display images, such as liquid crystal displays,plasma displays, organic EL displays, and projectors, but also displaysdesigned to transfer information by displaying letters, numbers, etc.

The details of the protective display film for displays are as describedabove.

Coating Agent

One embodiment of the present disclosure is a coating agent for forminga protective display film comprising a specific fluoropolymer.

The coating agent may comprise a fluoropolymer and an aprotic solvent.

The fluoropolymer in the coating agent may be the fluoropolymerdescribed above for the protective display film. Therefore, the detailsof the fluoropolymer for the protective display film are applicable tothe details of the fluoropolymer for the coating agent.

The content of the fluoropolymer in the coating agent can be, forexample, 5 mass % or more and 65 mass % or less, 10 mass % or more and65 mass % or less, 20 mass % or more and 65 mass % or less, 30 mass % ormore and 65 mass % or less, more than 30 mass % and 65 mass % or less,or 20 mass % or more and 40 mass % or less, based on the total mass ofthe coating agent. The content is preferably more than 20 mass % and 65mass % or less, more preferably 25 mass % or more and 60 mass % or less,and particularly preferably 30 mass % or more and 50 mass % or less.

The aprotic solvent in the coating agent may be the aprotic solventdescribed above for the protective display film. Therefore, the detailsof the aprotic solvent for the protective display film are applicable tothe details of the aprotic solvent for the coating agent.

The content of the aprotic solvent in the coating agent can be, forexample, 35 mass % or more and 95 mass % or less, 35 mass % or more and90 mass % or less, 35 mass % or more and 80 mass % or less, 35 mass % ormore and 70 mass % or less, 35 mass % or more and less than 70 mass %,or 60 mass % or more and 80 mass % or less, based on the total mass ofthe coating agent. The content is preferably 35 mass % or more and lessthan 80 mass %, more preferably 40 mass % or more and 75 mass % or less,and particularly preferably 50 mass % or more and 70 mass % or less.

The coating agent may comprise a polymerization initiator. Thepolymerization initiator for the coating agent may be the polymerizationinitiator described above for the protective display film. Therefore,the details of the polymerization initiator for the protective displayfilm are applicable to the details of the polymerization initiator forthe coating agent.

The content of the polymerization initiator in the coating agent is, forexample, 0.00001 mass % or more and 10 mass % or less, preferably0.00005 mass % or more and 10 mass % or less, and more preferably 0.0001mass % or more and 10 mass % or less, based on the total mass of thecoating agent.

The coating agent may comprise the fluoropolymer and an aprotic solvent,and optionally a polymerization initiator and optionally othercomponents, in appropriate amounts. Examples of other components caninclude refractive index adjusters, various fillers (e.g., electricallyconductive fillers), hardness-imparting agents, colorants,light-diffusing agents, plasticizers, viscosity modifiers,flexibilizers, light-resistant stabilizers, reaction inhibitors, andadhesion promoters. The content of the other components can be, forexample, 0.01 mass % or more and 50 mass % or less, preferably 0.01 mass% or more and 30 mass % or less, more preferably 0.01 mass % or more and20 mass % or less, based on the total mass of the coating agent.

The coating agent can be produced by mixing the fluoropolymer and anaprotic solvent, optionally with a polymerization initiator andoptionally with other components.

The coating agent can be produced by mixing a polymerization reactionmixture obtained by the solution polymerization of fluoropolymerdescribed above (this reaction mixture contains at least a fluoropolymerand an aprotic solvent) optionally with an aprotic solvent and/or othercomponents.

When solution polymerization is performed, the fluoropolymerconcentration or the amount of fluoropolymer dissolved in thepolymerization reaction mixture can be increased, and the step ofisolating the fluoropolymer from the polymerization reaction mixture canbe omitted. For this reason, the coating agent preferably contains apolymerization reaction mixture obtained by solution polymerization.

In the coating agent, the content of the polymerization reaction mixtureof solution polymerization can be appropriately selected according tothe concentration of the fluoropolymer in the polymerization reactionmixture and the functions, thickness, etc. of the film to be produced.The content of the polymerization reaction mixture of solutionpolymerization in the coating agent can be, for example, 5 mass % ormore and 100 mass % or less, preferably 20 mass % or more and 100 mass %or less, and more preferably 30 mass % or more and 100 mass % or less,based on the total mass of the coating agent.

The coating agent comprising an aprotic solvent in which thefluoropolymer is dissolved or dispersed can form a film, for example, byapplying the agent to a portion in which the formation of protectivefilm is required by an appropriate method (e.g., spray coating, dipcoating, bar coating, gravure coating, roll coating, ink jet, spincoating), and then removing the solvent by drying, heating, etc. Afterapplication of the coating agent, heating is preferably performed. Thedrying or heating temperature is, for example, 30° C. or higher and 150°C. or lower, and preferably 30° C. or higher and 80° C. or lower.

For example, a film can be formed by applying the coating agent of thepresent disclosure, followed by drying in a dryer at 80° C.Alternatively, after a fluoropolymer film is famed by applying thecoating agent of the present disclosure, one or more other componentsetc. that constitute a display can be formed on this film.

The present disclosure includes the following embodiments.

Item 1.

A protective display film comprising a fluoropolymer, wherein

the fluoropolymer comprises, as a main component, a monomer unitrepresented by formula (1):

wherein R¹ to R⁴ are each independently a fluorine atom, a fluoroalkylgroup, or a fluoroalkoxy group.

Item 2.

The protective display film according to Item 1, wherein thefluoropolymer further comprises a fluoroolefin unit.

Item 3.

The protective display film according to Item 2, wherein thefluoroolefin unit is at least one member selected from the groupconsisting of a fluorine-containing perhaloolefin unit, a vinylidenefluoride unit, a trifluoroethylene unit, a pentafluoropropylene unit,and a 1,1,1,2-tetrafluoro-2-propylene unit.

Item 4.

The protective display film according to Item 3, wherein thefluorine-containing perhaloolefin unit is at least one member selectedfrom the group consisting of a chlorotrifluoroethylene unit, atetrafluoroethylene unit, a hexafluoropropylene unit, a perfluoro(methylvinyl ether) unit, a perfluoro(ethyl vinyl ether) unit, aperfluoro(propyl vinyl ether) unit, a perfluoro(butyl vinyl ether) unit,and a perfluoro(2,2-dimethyl-1,3-dioxol) unit.

Item 5.

The protective display film according to Item 2, wherein thefluoroolefin unit is at least one member selected from the groupconsisting of a chlorotrifluoroethylene unit, a tetrafluoroethyleneunit, a hexafluoropropylene unit, a perfluoro(methyl vinyl ether) unit,and a perfluoro(propyl vinyl ether) unit.

Item 6.

The protective display film according to any one of Items 1 to 5, havingan average film thickness of 10 nm or more.

Item 7.

The protective display film according to any one of Items 1 to 6, havingan indentation hardness of 250 N/mm² or more and 1000 N/mm² or less.

Item 8.

The protective display film according to any one of Items 1 to 7, havingan indentation elastic modulus of 2.5 GPa or more and 10 GPa or less.

Item 9.

The protective display film according to any one of Items 1 to 8, havinga total light transmittance of 90% or more.

Item 10.

The protective display film according to any one of Items 1 to 9, havinga refractive index of 1.29 or more and 1.37 or less.

Item 11.

The protective display film according to any one of Items 1 to 10,having an Abbe number of 80 or more and 100 or less.

Item 12.

The protective display film according to any one of Items 1 to 11,having a water absorption at 24° C. of 0.1% or less.

Item 13.

The protective display film according to any one of Items 1 to 12,wherein the fluoropolymer has a glass transition temperature of 110° C.or higher.

Item 14.

A display comprising the protective display film of any one of Items 1to 13.

Item 15.

A coating agent for forming the protective display film of any one ofItems 1 to 13, the coating agent comprising a fluoropolymer and anaprotic solvent,

whereinthe fluoropolymer comprises, as a main component, a monomer unitrepresented by formula (1):

wherein R¹ to R⁴ are each independently a fluorine atom, a fluoroalkylgroup, or a fluoroalkoxy group.

Item 16.

The coating agent according to Item 15, wherein the content of thefluoropolymer is 20 mass % or more and 65 mass % or less based on thetotal mass of the coating agent.

Item 17.

The coating agent according to Item 15 or 16, wherein the aproticsolvent is at least one solvent selected from the group consisting ofperfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes,hydrofluorocarbons, perfluorocyclic ethers, hydrofluoroethers, andolefin compounds containing at least one chlorine atom.

Item 18.

The coating agent according to any one of Items 15 to 17, wherein theaprotic solvent is at least one hydrofluoroether.

Although embodiments are described above, it can be understood thatvarious modifications in form and details may be made without departingfrom the spirit and scope of the claims.

EXAMPLES

An embodiment of the present disclosure is described in more detailbelow with Examples; however, the present disclosure is not limited tothese.

The symbols and abbreviations in the Examples are used with thefollowing meanings.

Initiator solution (1): a methanol solution containing 50 mass %di-n-propyl peroxydicarbonate (10-hour half-life temperature: 40° C.)Fluoropolymer (1-11): a polymer composed of unit (1-11) Mw: mass averagemolecular weight

GPC Analysis Method (Measurement of Mass Average Molecular Weight ofFluoropolymer) Sample Preparation Method

A polymer was dissolved in perfluorobenzene to prepare a 2 mass %polymer solution, and the polymer solution was passed through a membranefilter (0.22 μm) to obtain a sample solution.

Measurement Method

Standard sample for measurement of molecular weight: polymethylmethacrylateDetection method: RI (differential refractometer)

Confirmation of Polymer Solubility

Whether the polymer was dissolved in the liquid was determined asfollows.

Each of the prepared liquids was visually observed, and when noundissolved polymer was observed and the entire liquid flowed uniformlyat room temperature, it was determined that the polymer was dissolved.

Average Film Thickness

The average film thickness was defined as the average value of athickness measured 5 times with a micrometer. When measuring thethickness of a film itself was difficult, such as when a film formed ona base material of a substrate etc. could not be peeled off, the averagefilm thickness was calculated by measuring the thickness of the basematerial before film formation and the thickness of the base materialafter film formation (the sum of the film thickness and the basematerial thickness) 5 times each with a micrometer, and subtracting theaverage value of the thickness before film formation from the averagevalue of the thickness after film formation.

Indentation Hardness and Indentation Elastic Modulus

The indentation hardness (H_(IT); indentation hardness) of the samplewas measured using an ENT-2100 ultra-fine hardness tester produced byNanotec Corporation. The indentation elastic modulus was also measuredat the same time. The test was performed by adjusting the indentationdepth to be 1/10 or less of the thickness.

Measurement Method for Total Light Transmittance and Haze

The total light transmittance and haze were measured using an NDH7000SPII haze meter (produced by Nippon Denshoku Industries Co., Ltd.)in accordance with JIS K7136 (haze value) and JIS K7361-1 (total lighttransmittance). A film with an average film thickness of 100 μm was usedas the sample to be measured. The sample was produced by coating a glassplate with a coating agent such that the thickness after drying was 100μm, performing drying at 80° C. for 4 hours, and peeling off theresulting dried film with an average film thickness of 100 μm from theglass plate.

Transmittance at Each Wavelength

The transmittance at a specific wavelength of a sample (a film with anaverage film thickness of 100 μm) was measured using a Hitachi U-4100spectrophotometer. An integrating sphere detector was used as thedetector.

Refractive Index

The refractive index of a sample at 23° C. was measured with an Abberefractive index meter (NAR-1T SOLID, produced by Atago Co., Ltd.). Thewavelength was a wavelength approximate to D-line because of the use ofthe LED attached to the device.

Abbe Number

The Abbe number of a sample at 23° C. was measured with an Abberefractive index meter (NAR-1T SOLID, produced by Atago Co., Ltd.).

Reflectance

An absolute specular reflector was attached to a Hitachi U-4100spectrophotometer, and the reflectance at 550 nm at 5° was measured.

Water Absorption (24° C.)

The weight of a sample that had been thoroughly dried beforehand wasmeasured and set as W0. The sample was then completely immersed in waterat 24° C. that was 100 times or greater than W0 by mass. The weight ofthe sample after 24 hours was measured and set as W24. The waterabsorption was determined according to the following formula.

Water absorption (%)=100×(W24−W0)/W0

Water Absorption (60° C.)

The weight of a sample that had been thoroughly dried beforehand wasmeasured and set as W0, and then completely immersed in water at 60° C.that was 100 times or greater than W0 by mass. The weight of the sampleafter 24 hours was measured and set as W24. The water absorption wasdetermined according to the following formula.

Water absorption (%)=100×(W24−W0)/W0

Tensile Elastic Modulus

A sample (length: 30 mm, width: 5 mm, thickness: 0.1 mm) was measuredwith a DVA220 dynamic viscoelasticity measurement device produced by ITMeasurement Control Co., Ltd., under the conditions of a tensile mode, agrip width of 20 mm, a measurement temperature of 25° C. to 150° C., atemperature-increasing rate of 2° C./min, and a frequency of 1 Hz. Theelastic modulus value at 25° C. was defined as a tensile elasticmodulus.

Tensile Strength

The tensile strength of a film was measured using an AGS-100NX autographproduced by Shimadzu Corporation. The sample was cut to a dumbbell shape5B as stated in JIS K7162. The measurement was performed under theconditions of a chuck-to-chuck distance of 12 mm, a crosshead speed of 1ram/min, and room temperature.

Thermal Decomposition Temperature

The temperatures at which the mass loss percentage of a sample became0.1% and 5% were measured at a temperature-increasing rate of 10°C./minute in an air atmosphere using a thermogravimetric-differentialthermal analyzer (Hitachi High-Tech Science Corporation; STA7200).

Glass Transition Temperature (Tg)

The temperature was increased (first run), decreased, and then increased(second run) at 10° C./minute in the temperature range of 30° C. orhigher and 200° C. or lower using a DSC (differential scanningcalorimeter; Hitachi High-Tech Science Corporation, DSC7000); themidpoint of the endothermic curve in the second run was determined to bethe glass transition temperature (° C.).

Coefficient of Linear Expansion

A thermomechanical analyzer (TMA8310; produced by Rigaku Corporation)was set in a tensile mode with a chuck-to-chuck distance of 15 mm. Asample cut to a size of 5 mm in width and 20 mm in length was held withthe chucks, and the temperature was increased from room temperature to150° C. (1st up), decreased to room temperature, and then increased to150° C. (2nd up) at 2° C./minute. The average coefficient of linearexpansion at 25° C. or higher and 80° C. or lower in the 2nd up wasdetermined and defined as the coefficient of linear expansion.

Preparation Example 1: Polymerization of Fluoropolymer Comprising Unit(1-11) as Main Component and Production of Polymer Solution(Polymerization Reaction Mixture)

The monomer (M1-11) (10 g), ethyl nonafluorobutyl ether (20 g) as asolvent, and the initiator solution (1) (0.041 g) were placed in a 50-mLglass container, and a polymerization reaction was then performed for 20hours while the mixture was heated such that the internal temperaturewas 40° C., thereby producing a fluoropolymer (1-11) (9.0 g, Mw: 97533).The fluoropolymer in the polymerization reaction mixture was dissolved,and the concentration was 31 mass %.

The weight of the polymer in the composition was measured by distillingoff the unreacted starting material, the solvent, the initiator residue,and the impurities contained in a trace amount in the monomer by vacuumdrying at 120° C. after the completion of the polymerization reaction.

Comparative Preparation Example 1: Production of Teflon (RegisteredTrademark) Solution

Teflon (registered trademark) AF1600 (2.0 g, Mw: 229738), which is acommercially available fluoropolymer, was added to methylnonafluorobutyl ether (8.0 g), and the mixture was stirred at roomtemperature for 2 days to prepare a uniformly dissolved solution.

Teflon (registered trademark) AF1600 contains the monomer unitrepresented by the following formula (10) and the monomer unitrepresented by the following formula (20) in a ratio of 65:35 (molarratio).

Example 1

The polymerization reaction mixture obtained in Preparation Example 1was directly used as a coating agent, and a protective display film wasproduced as follows.

A glass substrate was coated with the coating agent such that thethickness after drying was 100 μm, and drying was performed at 80° C.for 4 hours to form a transparent film. The film was then peeled offfrom the glass plate, thereby obtaining a fluoropolymer (1-11) film withan average film thickness of 100 μm.

The optical properties of the obtained film were measured. The resultsare shown below. Further, FIG. 1 shows the transmittance at eachwavelength.

Total light transmittance: 96%

Haze: 0.34%

Transmittance (193 nm): 74.4%

Transmittance (550 nm): 94.6%

Refractive index: 1.335

Abbe number: 91

Reflectance (550 nm): 0.62%

The obtained film had sufficient transmittance over the entirewavelength range and was thus confirmed to be suitable for use inprotecting displays. In addition, the film had a very low refractiveindex and a very low reflectance, and was thus confirmed to be usefulfor anti-reflection for displays.

The following items of the obtained film were also measured. The resultsare shown below.

Indentation hardness: 420 N/mm²

Indentation elastic modulus: 3.3 GPa

Water absorption (24° C.): 0.00%

Water absorption (60° C.): 0.09%

Tensile elastic modulus: 3.1 GPa

Tensile strength: 20.9 MPa

Thermal decomposition temperature (0.1%): 294.5° C.

Thermal decomposition temperature (5%): 439.4° C.

Glass transition temperature: 129° C.

Coefficient of linear expansion: 80 ppm

The obtained film had high indentation hardness and high indentationelastic modulus, and thus exhibited high hardness. Therefore, theobtained film had high scratch resistance and was thus confirmed to beuseful as a protective film.

The obtained film had a low water absorption and was thus confirmed toachieve a reduction in the expansion due to water absorption and inchange in the refractive index due to water absorption. The waterabsorption of general-purpose optical resin, e.g., polymethylmethacrylate, is about 2%.

Comparative Example 1: Film Formed from Teflon (Registered Trademark)AF1600

A film was formed using the fluoropolymer solution obtained inComparative Preparation Example 1 as a coating agent. A glass substratewas coated with the coating agent, and drying was performed at 80° C.for 4 hours. The film was then peeled off from the glass plate, therebyobtaining a transparent film with an average film thickness of 50 μm.The indentation hardness and indentation elastic modulus of the obtainedfilm were 145 N/mm² and 2 GPa, respectively, which were lower than thevalues of Example 1.

1. A protective display film comprising a fluoropolymer, wherein thefluoropolymer comprises, as a main component, a monomer unit representedby formula (1):

wherein R¹ to R⁴ are each independently a fluorine atom, a fluoroalkylgroup, or a fluoroalkoxy group.
 2. The protective display film accordingto claim 1, wherein the fluoropolymer further comprises a fluoroolefinunit.
 3. The protective display film according to claim 2, wherein thefluoroolefin unit is at least one member selected from the groupconsisting of a fluorine-containing perhaloolefin unit, a vinylidenefluoride unit, a trifluoroethylene unit, a pentafluoropropylene unit,and a 1,1,1,2-tetrafluoro-2-propylene unit.
 4. The protective displayfilm according to claim 3, wherein the fluorine-containing perhaloolefinunit is at least one member selected from the group consisting of achlorotrifluoroethylene unit, a tetrafluoroethylene unit, ahexafluoropropylene unit, a perfluoro(methyl vinyl ether) unit, aperfluoro(ethyl vinyl ether) unit, a perfluoro(propyl vinyl ether) unit,a perfluoro(butyl vinyl ether) unit, and aperfluoro(2,2-dimethyl-1,3-dioxol) unit.
 5. The protective display filmaccording to claim 2, wherein the fluoroolefin unit is at least onemember selected from the group consisting of a chlorotrifluoroethyleneunit, a tetrafluoroethylene unit, a hexafluoropropylene unit, aperfluoro(methyl vinyl ether) unit, and a perfluoro(propyl vinyl ether)unit.
 6. The protective display film according to claim 1, having anaverage film thickness of 10 nm or more.
 7. The protective display filmaccording to claim 1, having an indentation hardness of 250 N/mm² ormore and 1000 N/mm² or less.
 8. The protective display film according toclaim 1, having an indentation elastic modulus of 2.5 GPa or more and 10GPa or less.
 9. The protective display film according to claim 1, havinga total light transmittance of 90% or more.
 10. The protective displayfilm according to claim 1, having a refractive index of 1.29 or more and1.37 or less.
 11. The protective display film according to claim 1,having an Abbe number of 80 or more and 100 or less.
 12. The protectivedisplay film according to claim 1, having a water absorption at 24° C.of 0.1% or less.
 13. The protective display film according to claim 1,wherein the fluoropolymer has a glass transition temperature of 110° C.or higher.
 14. A display comprising the protective display film ofclaim
 1. 15. A coating agent for forming the protective display film ofclaim 1, the coating agent comprising a fluoropolymer and an aproticsolvent, wherein the fluoropolymer comprises, as a main component, amonomer unit represented by formula (1):

wherein R¹ to R⁴ are each independently a fluorine atom, a fluoroalkylgroup, or a fluoroalkoxy group.
 16. The coating agent according to claim15, wherein the content of the fluoropolymer is 20 mass % or more and 65mass % or less based on the total mass of the coating agent.
 17. Thecoating agent according to claim 15, wherein the aprotic solvent is atleast one solvent selected from the group consisting ofperfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes,hydrofluorocarbons, perfluorocyclic ethers, hydrofluoroethers, andolefin compounds containing at least one chlorine atom.
 18. The coatingagent according to claim 15, wherein the aprotic solvent is at least onehydrofluoroether.